ABSTRACTChitosan is a naturally occurring cationic polysaccharide and has attracted much attention in the past decade as an important ophthalmic biomaterial. We recently demonstrated that the genipin (GP) cross-linked chitosan is compatible with human retinal pigment epithelial cells. The present work aims to further investigate the in vivo biocompatibility of GP-treated chitosan (GP-chi group) by adopting the anterior chamber of a rabbit eye model. The glutaraldehyde (GTA) cross-linked samples (GTA-chi group) were used for comparison. The 7-mm-diameter membrane implants made from either non-cross-linked chitosan or chemically modified materials with a cross-linking degree of around 80% were inserted in the ocular anterior chamber for 24 weeks and characterized by slit-lamp and specular microscopic examinations, intraocular pressure measurements, and corneal thickness measurements. The interleukin-6 expressions at mRNA level were also detected by quantitative real-time reverse transcription polymerase chain reaction. Results of clinical observations showed that the overall ocular scores in the GTA-chi groups were relatively high. In contrast, the rabbits bearing GP-chi implants in the anterior chamber of the eye exhibited no signs of ocular inflammation. As compared to the non-cross-linked counterparts, the GP-chi samples improved the preservation of corneal endothelial cell density and possessed better anti-inflammatory activities, indicating the benefit action of the GP cross-linker. In summary, the intracameral tissue response to the chemically modified chitosan materials strongly depends on the selection of cross-linking agents.

f4-ijms-13-10970: Specular microscopy measurements of corneal endothelial cell density 24 weeks after surgical insertion of various chitosan implants in the ocular anterior chamber. The dash line represents the preoperative cell density. An asterisk indicates statistically significant differences (*p < 0.05; n = 6) as compared to the Ctrl (sham-operated) groups. N/A: Not applicable, because the biological responses are too severe to be observed.

Mentions:
Figure 4 shows the results of quantitative specular microscopic analysis of rabbit corneal endothelium. At pre-operation, the mean corneal endothelial cell density was approximately 3200 cells/mm2. No significant difference was noted in the cell density of Ctrl groups (3145 ± 71 cells/mm2) compared with the values before surgery (p > 0.05). After exposure to the Chi implants for 24 weeks, the animals had a significantly lower cell density (2998 ± 63 cells/mm2). Because the biological responses were too severe to be observed, the endothelial cell counts of GTA-chi groups were not available from specular microscopic images. The cell density did not show a significant difference between the sham-operated and GP-chi groups (3172 ± 90 cells/mm2; p > 0.05).

f4-ijms-13-10970: Specular microscopy measurements of corneal endothelial cell density 24 weeks after surgical insertion of various chitosan implants in the ocular anterior chamber. The dash line represents the preoperative cell density. An asterisk indicates statistically significant differences (*p < 0.05; n = 6) as compared to the Ctrl (sham-operated) groups. N/A: Not applicable, because the biological responses are too severe to be observed.

Mentions:
Figure 4 shows the results of quantitative specular microscopic analysis of rabbit corneal endothelium. At pre-operation, the mean corneal endothelial cell density was approximately 3200 cells/mm2. No significant difference was noted in the cell density of Ctrl groups (3145 ± 71 cells/mm2) compared with the values before surgery (p > 0.05). After exposure to the Chi implants for 24 weeks, the animals had a significantly lower cell density (2998 ± 63 cells/mm2). Because the biological responses were too severe to be observed, the endothelial cell counts of GTA-chi groups were not available from specular microscopic images. The cell density did not show a significant difference between the sham-operated and GP-chi groups (3172 ± 90 cells/mm2; p > 0.05).

ABSTRACTChitosan is a naturally occurring cationic polysaccharide and has attracted much attention in the past decade as an important ophthalmic biomaterial. We recently demonstrated that the genipin (GP) cross-linked chitosan is compatible with human retinal pigment epithelial cells. The present work aims to further investigate the in vivo biocompatibility of GP-treated chitosan (GP-chi group) by adopting the anterior chamber of a rabbit eye model. The glutaraldehyde (GTA) cross-linked samples (GTA-chi group) were used for comparison. The 7-mm-diameter membrane implants made from either non-cross-linked chitosan or chemically modified materials with a cross-linking degree of around 80% were inserted in the ocular anterior chamber for 24 weeks and characterized by slit-lamp and specular microscopic examinations, intraocular pressure measurements, and corneal thickness measurements. The interleukin-6 expressions at mRNA level were also detected by quantitative real-time reverse transcription polymerase chain reaction. Results of clinical observations showed that the overall ocular scores in the GTA-chi groups were relatively high. In contrast, the rabbits bearing GP-chi implants in the anterior chamber of the eye exhibited no signs of ocular inflammation. As compared to the non-cross-linked counterparts, the GP-chi samples improved the preservation of corneal endothelial cell density and possessed better anti-inflammatory activities, indicating the benefit action of the GP cross-linker. In summary, the intracameral tissue response to the chemically modified chitosan materials strongly depends on the selection of cross-linking agents.